| Electron spectroscopy technique has widely been used for elemental analysis, chemical state analysis and topography measurement on a solid surface, therefore it plays an important role in the research of surface physics. In recent years, the studies about plasmon excitation on single nanoparticle and excitation spectra of individual biological macromolecules require the electron spectroscopy measurements of surface with nanometer spatial resolutions (i.e. surface spectroscopic mapping). Although by using the rapidly developing scanning transmission electron microscopy (STEM), people can already acquire electron energy spectroscopy with atomic spatial resolution, the high-energy electron beam employed in STEM will cause radiation damages to the samples, especially organic or biological molecules. Meanwhile, the samples need to be very thin, which limits the application of STEM.Another devised route for obtaining spatially resolved spectroscopic information is the employment of near-field detection techniques which can be achieved by combining the electron energy spectroscopy with the scanning tunneling microscope (STM). The combination instrument can work in STM mode for surface topography measurement and scanning probe electron energy spectroscopy (SPEES) mode for electron energy spectroscopy measurement. In this dissertation, we describe the setting up of the scanning probe electron energy spectrometer which combines a double toroidal analyzer with an ultrahigh vacuum STM, and the research performed on the instrument is also presented. The dissertation composes of the following 5 chapters:In the first chapter, we introduce the recent development of the spatially resolved spectroscopy techniques and discuss about the restrictions of the widely used electron microscope. Considering that the high spatial resolution can also be achieved by the near-field detection techniques, one can combine the electron spectroscopy with a STM to obtain spatially resolved spectroscopic information. We also introduce the attempts made by several international research groups to develop this technique.In chapter 2, a novel home-made SPEES apparatus will be described which consists of ultrahigh vacuum system, the tip-sample replacement and transfer system, STM unit, electron energy analysis and detection system, damping devices and magnetic shielding.In chapter 3 the details of the design, machining, manufacturing of the STM unit employed in the spectrometer and the STM control software developed based on LabVIEW language is presented. The STM was tested in the atmosphere using platinum-iridium alloy tips and highly oriented pyrolytic graphite (HOPG) samples, and the atomic resolution images and nanostructure images of graphite were both obtained.In chapter 4, we describe the adjustment of the SPEES apparatus, including the acquisition of the ultrahigh vacuum environment, the calibration of the electron energy analyzer combined with the STM and the treatment of the field emission STM tips. We measured the topography and electron energy loss spectroscopy (EELS) of HOPG and Ag film samples using SPEES and obtained the information of surface plasmons (SP) in situ which was similar as the results acquired by other groups.Finally, in the last chapter, the spatial resolution of spectroscopic mapping by SPEES is determined. It was found that the field emission electron beam can be used to modify the nanostructure of the unannealed Ag film samples, and the bombard of electron beam on surface will cause the decreasing of the intensity of the SP peak in EELS. With this nanofabrication method we prepared a sample in situ and took a one-dimensional scanning spectroscopy measurement on it. By comparing the intensity of EELS of Ag SP from the modified and non-modified area on the Ag film sample, the spatial resolution of SPEES is determined to be around 0.7-0.8μm. |
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